The present invention relates to elastic actuator control apparatus and method that control the operation of an elastic actuator such as a hydropneumatic drive actuator driven by deformation of an elastic body. The present invention also relates to elastic actuator drive-type movable mechanism control apparatus and method that control a movable mechanism driven by the elastic actuator.
Recently, domestic robots such as a pet robot are actively developed, and practical realization of the practical domestic robots such as a household assistance robot is expected in the future. Because it is necessary that the domestic robot go in a home to live with a human, the domestic robot differs from the conventional industrial robot and the like in the required specifications.
In the industrial robot, an electric motor and a speed reducer are used, and high hand position accuracy of repeatability of 0.1 mm or the like is realized by high-gain feedback control. However, because a mechanism driven by the electric motor often has high rigidity and poor flexibility, there are many issues from a safety standpoint.
On the other hand, the high accuracy of the repeatability of 0.1 mm or the like is not always necessary in the domestic robot, but the safety is emphasized such that the domestic robot does no injury to a human when the domestic robot comes into contact with the human. Accordingly, the electric-motor driven mechanism used in the conventional industrial robot is not suitable to the domestic-robot field in which the safety is emphasized, and the flexible and safe robot arm is required.
In order to solve the above issues, for example, there has been proposed a robot arm in which a McKibben type pneumatic actuator is utilized. In a configuration of the McKibben type pneumatic actuator, constraint means including a fiber cord is arranged in an outer surface of a tubular elastic body made of a rubber material, and both end portions of the tubular elastic body are adapted to be sealed in an air-tight manner with sealing members. When internal pressure is applied to an internal space of the tubular elastic body through fluid injection/discharge means using a compressible fluid such as air, although the tubular elastic body may try to be mainly expanded in a radial direction, the expansion is transformed into motion in a central axis direction of the tubular elastic body by action of the constraint means, which contracts a total length of the tubular elastic body. Because the McKibben type actuator is mainly formed by an elastic body, the McKibben type actuator has advantages such as the flexibility, the safety, and light weight.
However, the hydropneumatic drive actuator such as the McKibben type actuator, which is operated by the fluid pressure such as air, has an issue that generally the elastic actuator is difficult to control, for example, in the elastic actuator, the responsivity is worsened due to the elastic property generated by the fluid compressibility, the influence of the channel resistance etc., and the like.
Conventionally, in order to solve the issue, Japanese Examined Patent No. 2583272 discloses a control apparatus in which a desired track can be drawn by including a delay circuit for the robot arm driven by combination of a servomotor and a hydropneumatic drive actuator.
However, in the above control apparatus including the delay circuit, since the delay is always generated for a desired operation, responsivity is worsened and the work necessary to be processed in real time cannot be performed. The control apparatus exerts the effect only in the case of the combination of the servomotor and the fluid drive actuator, and the control apparatus cannot exert the effect in the robot arm including only the fluid drive actuator.
An object of the present invention is to resolve the foregoing issues and provide elastic actuator control apparatus and method, by which a movable mechanism such as a robot arm driven by an elastic actuator can be controlled with good responsivity and the position arid force can be controlled with high accuracy.